1. Field of the Invention
The present invention relates to an optical apparatus that includes an actuator configured to drive a photographic lens in an optical-axis direction. More specifically, the present invention relates to a vibratory (vibration-type) linear actuator.
2. Description of the Related Art
An optical apparatus discussed in Japanese Patent Application Laid-Open No. 10-90584 includes a vibratory linear actuator as a driving source of a lens.
The vibratory linear actuator discussed in Japanese Patent Application Laid-Open No. 10-90584 includes a vibration member and a contact member. The vibration member has an electro-mechanical energy conversion function for generating vibration according to an electric signal. The contact member contacts the vibration member.
The vibration member is fixed to a lens-holding member, while the contact member is fixed to a stationary member of a lens barrel. When the vibration member generates the driving vibration, the vibration member and the lens-holding member move together.
Alternatively, the contact member is fixed to the lens-holding member and the vibration member is fixed to a stationary member of the lens barrel. When the vibration member generates the driving vibration, the contact member and the lens-holding member move together.
FIGS. 24A to 24D illustrate exemplary vibratory linear actuators discussed in Japanese Patent Application Laid-open No. 10-90584. The vibratory linear actuators include a lens-holding frame 1 that holds a lens, and a guide bar 2 that guides the lens-holding frame 1 in an optical-axis direction.
A support member 3 supports a vibration member 4. A contact member 5 and the vibration member 4 are in a press-contact state. A resilient member 6 generates a pressing force for bringing the vibration member 4 into contact with the contact member 5.
A lens barrel illustrated in FIG. 25 includes a lens-holding frame 11 that holds a lens. A guide bush 12, attached to the lens-holding frame 11, can move in the optical-axis direction along a guide bar 13. A vibrator-supporting frame 14 is provided on the guide bush 12. A pair of support members 15a and 15b supports a vibration member 16.
A contact member 17 is fixed to a lens-barrel body 18. A spring 19 resiliently presses the vibration member 16 to the contact member 17.
According to the examples of FIGS. 24A and 24B, only the resilient member 6 supports the vibration member 4 or the contact member 5, although the vibration member 4 and the contact member 5 are kept in a press-contact state. No member supports the vibration member 4 or the contact member 5 in the optical-axis direction. In a lens driving operation, the resilient member 6 may deform in a driving direction and positioning of the lens-holding frame 1 may not be accurate.
According to the examples of FIGS. 24C and 24D, the support member 3 holds the vibration member 4 that can move in a direction perpendicular to a press-contact surface. Similarly, according to the example of FIG. 25, the support members 15a and 15b hold the vibration member 16 that can move in a direction perpendicular to a press-contact surface. If the installation of the guide bar (2, 13), the support member (3, 15a, 15b), and the contact member (5, 17) are inadequate, undesirable inclination may generate between these components. The vibration member (4, 16) and the contact member (5, 17) are brought into a point- or line-contact state.
The vibration member and the contact member in such a point- or line-contact state cannot generate a sufficient driving force as expected.
FIG. 26B illustrates a slider 21 in an inclined state relative to a vibrator 22, when seen from the optical-axis direction. A pressure-receiving surface of the slider 21 is a flat surface. L represents a width of the pressure-receiving surface of the slider 21. φ represents a relative inclination between the pressure-receiving surface of the slider 21 and a pressure-receiving surface of the vibrator 22.
FIG. 26A illustrates the slider 21 and the vibrator 22 respectively in a surface contact state with no relative inclination (i.e., φ=0) wherein the slider 21 has a flat pressure-receiving surface and the vibrator 22 has a flat pressure-receiving surface. The pressing force distributes uniformly. The vibratory linear actuator can operate with performances expected.
Durability of the vibratory linear actuator greatly depends on a press-contact force acting on the pressure-receiving surfaces of the slider 21 and the vibrator 22. As described above, the vibratory linear actuator performs a frictional driving operation using an elliptic motion generated on the pressure-receiving surface of the vibrator 22 and the pressing force acting between the slider 21 and the vibrator 22.
In this frictional driving operation, abrasion may arise on the pressure-receiving surfaces of the slider 21 and the vibrator 22. The abrasion is a factor determining the durability.
If the force acting between the slider 21 and the vibrator 22 is uniform and appropriate, the vibratory actuator can possess sufficient durability.
However, as illustrated in FIG. 26B, there may be relative inclination φ between the slider 21 and the vibrator 22 in an actual product due to manufacturing differences and assembling errors.
In this case, only one edge of the slider 21 contacts the vibrator 22. A frictional force generated between the slider 21 and the vibrator 22 is insufficient. Performances of the vibratory linear actuator deteriorate significantly.